Looping pits and operating methods for looping pits are generally known. In the prior art, the strip is supplied to the looping pit at a pit entrance. The strip is emitted from the looping pit at a pit exit. The drag in the strip is detected by means of a drag measurement device. The drag measurement device may alternatively be arranged at the pit entrance or at the pit exit. The detected drag is supplied to a control device. The control device readjusts a pit state of the looping pit on the basis of the detected drag.
The looping pit may also have driven rollers which are arranged between the pit entrance and the pit exit. The control device can determine control signals for these rollers, and can emit these control signals to the driven rollers. The driven rollers in this case act on the strip which is buffered in the looping pit, corresponding to the control signals.
Looping pits for strips generally have a multiplicity of rollers, wherein the strip loops alternately around the upper side and the lower side of the rollers, from one roller to another. The heights of the rollers can be adjusted with respect to one another. The length of the strip section which is buffered by the looping pit can be varied by adjusting the vertical distance between the rollers. The vertical distance is normally adjusted by moment control or speed control as a function of a nominal filling level of the looping pit. If driven rollers are driven between the pit entrance and the pit exit, the rollers are subject to individual moment control or speed control as a function of the moment or speed nominal value with which the vertical distance is set and as a function of an entrance speed and/or an exit speed at which the strip is supplied to and emitted from the looping pit.
If the moment or the speed by means of which the vertical distance between the rollers is set is set incorrectly, this incorrect setting influences the drag in the strip section which is located in the looping pit. Drag influences such as these can have negative effects on devices which are arranged downstream from the looping pit. In the prior art, in order to avoid drag fluctuations, the drag is detected—for example on the exit side—and is supplied to the control device. The control device corrects the vertical adjustment speed as a function of the detected drag.
The looping pit according to the prior art already operates quite well. However, its method of operation can be improved.